DESCRIPTION: Dr. Kunert's research interest is the role of oxygen in regulating vascular reactivity as it might relate to the development of hypertension. Her previous work examined the relationship between O2 availability (oxy-hemoglobin affinity) and vascular tone in terms of regional and systemic changes in blood flow. The current project will focus on O2 induced changes in resistance at the microcirculatory level and the expression of an enzyme that inhibits the formation of 20-hydroxyeicosatetraenoic acid (20-HETE), which may mediate the constriction of arterioles exposed to elevated pO2. The work will be conducted in the lab of Dr. Lombard at the Medical College of Wisconsin in Milwaukee. These skills and techniques will broaden the applicants repertoire of research skills, giving her several avenues by which to explore vessel reactivity. The animal models of interest are the Goldblatt model of rats with 1-kidney 1-clip, and the Grollman model of hypertension in hamsters. The involvement of 20-HETE in the response to )2 will be determined by administration of 17 octadecenoic acid, which inhibits CYP4A (cytochrome P450 4A). A central assumption in the proposal is that sufficient CYP4A exists in endothelial cells, smooth muscle cells, or surrounding parenchyma, to produce the 20-HETE needed for vasoconstriction in each different microvascular region. The cellular location of CyP4a will be identified by microdissection followed by PCR, and by microdissection, gel electrophoresis and Western blotting. Another assumption of the proposal is the CYP4a levels will be higher in hypertensive animals than in controls, which will explain the enhanced )2 sensitivity of hypertensive animals. Arterioles of hypertensive animals will be tested for their response to 20-HETE, both in situ and in vitro. The microvascular distribution of CYP4A in the cremaster muscle and the hamster cheek pouch will be determined by microdissection, Western blotting and PcR. The responses of the microvasculature of hypertensive animals to )2 tension will be examined with intravital microscopy. The proposed studies will involve approximately 260 adult male Sprague-Dawley rats, and an unspecified number of male hamsters with Grollman hypertension. The surgical procedures for the hypertensive procedures, microcirculatory preparation, and measurement techniques are described. All data will be presented as mean + 1 SE. Significant differences in values in the same animals will be evaluated by analysis of variance with repeated measures followed by post-hoc procedures. Non-parametric variables will be analyzed by nonparametric sign test (Western blots and standard RT-PCR measures).